Laminating apparatus

ABSTRACT

The present invention provides a laminating apparatus comprising a sheet transporter for transporting a sheet, a laminating film transporter for transporting at least one laminating film in such a manner that the laminating film is superposed with at least one surface of the sheet transported by the sheet transporter. A pressing mechanism means presses the sheet and the lamenting film or films in a mutually superposed state, a heater heats the laminating film, heat capacity detector detects the heat capacity of at least one of the laminating film or films and the sheet, and a controller controls at least one of the heater and the laminating film transporter, according to a detection signal from the heat capacity detector.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an apparatus for lamination bysandwiching an object between upper and lower heat-reactive laminatingfilms and applying heat and pressure thereto.

2. Related Background Art

Lamination is used for various objects for improving the appearance orpreservability thereof. FIG. 10 shows a conventional laminatingapparatus used for such lamination.

FIG. 10 is a longitudinal cross-sectional view of a conventionallaminating apparatus, wherein shown are an upper heat-reactivelaminating film 100 and a lower heat-reactive laminating film 100'.These films are respectively rolled as an upper sheet roll 101 and alower sheet roll 101'. Said laminating films 100, 100' respectively wraparound a heating roller 102 and a pressure roller 102' and are pulled atthe front ends by pull rollers 103, 103' for giving a predeterminedtension to said films. At the centers of said heating roller 102 andpressure roller 102' there are respectively provided heaters 104, 104'for heating said rollers.

At the downstream side (left side in FIG. 10) of said pull rollers 103,103', there is provided a cutter 105 for cutting the front and rear endsof the object after lamination.

A feed table 106 is provided for supporting an object 107 to belaminated, which is inserted, along the feed table 106, into the nip ofthe heating roller 102 and the pressure roller 102', where the upperlaminating film 100 and the lower laminating film 100' mutually meet.

On said laminating apparatus there is provided an operation unit,including switches 108, 109 for manually setting the transporting speedof the heating roller 102, pressure roller 102' and pull rollers 103,103', and the peripheral temperature of the heating roller 102 andpressure roller 102'.

However such conventional laminating apparatus has been associated witha drawback that lamination of satisfactory appearance cannot be obtainedunless the operator manually regulates the transporting speed of thelaminating films 100, 100' and the object and/or the temperature of theheating roller 102 and the pressure roller 102' according to the densityand thickness of the object to be laminated and the thickness of thelaminating films 100, 100'.

Also if the above-mentioned regulation fails, the object to be laminatedmay be unrecoverably damaged. Furthermore, the laminating films 100,100' are wasted at each regulation so that the operation is veryuneconomical.

SUMMARY OF THE INVENTION

In consideration of the foregoing, the object of the present inventionis to provide a laminating apparatus capable of lamination ofsatisfactory appearance in an automatic manner.

The present invention maintains optimum heating and other processingconditions, so that lamination of satisfactory appearance can beachieved in an automatic manner. Also the laminating apparatus can beused reliably without damage to the object to be laminated. Furthermorethe running cost of the apparatus can be economically reduced since thelaminating films can be utilized without waste.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal cross-sectional view of a laminating apparatusembodying the present invention, mounted on an image forming apparatus;

FIG. 2 is a lateral view of a sheet thickness detecting mechanismprovided a registration rollers;

FIGS. 3A and 3B are partial cross-sectional views of a sheet roll;

FIG. 4 is a developed view of a driving system of the laminatingapparatus;

FIG. 5 is a block diagram of a control circuit, for explaining thefunction of the laminating apparatus;

FIG. 6 is a longitudinal cross-sectional view of another embodiment ofthe present invention;

FIG. 7 is a perspective view showing the structure of a bubble jetrecording head;

FIGS. 8A to 8G are views showing the working principle of the bubble jetrecording head;

FIG. 9 is a longitudinal cross-sectional view of still anotherembodiment; and

FIG. 10 is a longitudinal cross-sectional view of a conventionallaminating apparatus.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following there will be explained an embodiment of the presentinvention, with reference to the attached drawings.

FIG. 1 is a longitudinal cross-sectional view of a laminating apparatusof the present invention, mounted on an image forming apparatus.

In a reader A, an original document placed on a platen glass 1 isilluminated by the light from an illuminating lamp 2, and the reflectedlight is guided by mirrors 3, 4 and focused by a lens 5 onto a CCD 6 forreading the original image. The image information of the image read bysaid reader A is transmitted to a printer B, and is recorded by ascanner 7 on a photosensitive drum 8 as an electrostatic latent image,which is developed by a developing unit 8a into a toner image.

On the other hand, transfer sheets 10 contained in a sheet cassette 9 inthe printer B are fed one by one by a sheet feed roller 11, and thetoner image on the photosensitive drum 8 is transferred, in a transferunit 12, onto the transfer sheet 10, which is subsequently dischargedfrom the printer B by a conveyor belt 13 and discharge rollers 14.

A laminating apparatus C of the present invention is detachably mounted,by a latch mechanism 15, on the main body of the image formingapparatus.

In said laminating apparatus, a flapper 16, driven by a solenoid 70(FIG. 5), selects whether or not to effect lamination according to thestate of a selector switch 17 (FIG. 5) provided in an operation unit onthe outer casing of said laminating apparatus C. More specifically, inresponse to an instruction for non-lamination entered from the operationunit 17, the flapper 16 assumes a broken-line position in FIG. 1 todeflect the transfer sheet 10 to a nonlamination path 18, whereby saidsheet 10 is discharged by discharge rollers 19 onto a sheet tray 20. Onthe other hand, in response to an instruction for lamination enteredfrom the operation unit 17, the flapper 16 assumes a solid-line positionin FIG. 1 to guide the sheet 10 into a lamination path 21 leading to alamination unit.

As said discharged sheet tray 20 is provided on the upper face of thelaminating apparatus C, constituting a part of the outer casing of saidapparatus with open space above, the transfer sheets 10 stacked on saidtray 20 can be easily removed. Also the space of the apparatus isreduced as said tray 20 is integrally constructed with the laminatingapparatus C.

In FIG. 1, registration rollers 22, 22' are provided for adjusting thetiming of the leading end of the transfer sheet 10 prior to the transferto the laminating unit, and correcting skewed feed of the transfer sheet10 released from the image forming apparatus, by forming a loop in thelamination path 21. Immediately in front of said registration rollers22, 22', there is provided a pre-registration sensor 23, composed of areflective photosensor, for detecting the edge of the transfer sheet 10.

A transfer path 24 for transferring the sheet 10 from the registrationrollers 22, 22' to the laminating unit is composed of upper and lowerguide plates 24a, 24b. Behind the upper guide plate 24a there isprovided a sheet heater 25 for heating said upper guide plate 24a whensaid heater is on, whereby the sheet 10 is dried prior to thelamination. Said sheet heater 25 can be arbitrarily turned on or off bya selector switch of the operation unit 17, according to the whether ornot to heat the transfer sheet 10.

Between said registration rollers 22, 22' and the sheet heater 25 thereis provided a density detecting sensor 26, composed of a photosensor,for detecting the density of the image on the sheet 10. The on/offcontrol of said sheet heater 25 may be conducted according to theinformation on the image density.

Rolls 27, 27' of laminating films 28, 28' are respectively providedabove and below. Laminating heaters 29, 29', for respectively heatingsaid laminating films 28, 28', have a curved shape in order to heat saidfilms over a wide area, and may be provided with sensors thereon forvarying the heating temperature.

Pressure rollers 30, 30' are provided for pressing therebetween thelaminating films 28, 28' heated by said heaters 29, 29' therebylaminating the transfer sheet 10. Separating fingers 31, 31' areconstantly maintained in friction contact with the periphery of thepressure rollers 30, 30' for peeling the laminating films 28, 28' fromthe pressure rollers 30, 30' when said films stick to said rollers. Atleast one of said pressure rollers 30, 30' may be provided a heatertherein for simultaneously effecting heating and pressing.

A cutter unit 33, composed of a cutter blade 34, a die 35 and a cuttermotor (not shown), is provided for cutting the front and rear ends ofthe laminated transfer sheet.

A lamination sensor 32, consisting of a reflective photosensor, isprovided for detecting the front and rear ends of the laminated transfersheet 10. Pull rollers 36, 36' have a peripheral speed larger than thatof the pressure rollers 30, 30' so that the laminated transfer sheet 10is subjected to a predetermined tension between said pull rollers 36,36' and the pressure rollers 30, 30'.

Said sheet rolls 27, 27' are respectively given a load in the filmdrawing direction, so that the laminating films 28, 28' pulled by thepull rollers 36, 36' are given a tension between said pull rollers 36,36' and the sheet rolls 27, 27' by means of the pressure rollers, 30,30' and the heaters 29, 29'.

A waste case 39 is provided for receiving waste chips (laminated filmarea not containing the transfer sheet 10) of the laminating films 28,28' cut by the cutter unit 33. Said case 39 can be pulled out forwardfrom the apparatus, so that the waste chips in said case can bedischarged when said case becomes full. Discharge rollers 37, 37' areprovided for discharging the laminated transfer sheet 10 from thelaminating apparatus C onto a laminate tray 38.

In the following the details of the units of the laminating apparatus Cwill be explained with reference to FIGS. 2 to 4.

At first there will be explained the details of the aforementionedregistration rollers 22, 22' with reference to FIG. 2, which is alateral view of a sheet thickness detecting mechanism provided at saidregistration rollers. The shaft 22a of the registration roller 22engages with an end of a sheet thickness detecting lever 40, whichtherefore rotates about a rotating shaft 41 when the transfer sheet 10enters the nip between the registration rollers 22, 22'. Said lever isprovided with a lever flag 41", and the lengths of arms of said lever 40are so selected as to satisfy a relation l₁ >l₂, so that the amount ofmovement of the registration roller 22 is converted into an, amplifiedamount of movement of said lever flag 41". Opposed to said lever flag41" there is provided a sheet thickness sensor 43, composed of aphotosensor, which linearly detects the amount of movement of the leverflag 41", thereby detecting the thickness of the transfer sheet 10passing through the nip of the registration rollers 22, 22'.

In the following there will be explained the details of the sheetrollers 27, 27" with reference to FIGS. 3A, 3B which are partialcross-sectional views thereof. The sheet roll 27 is wound on a core 44which is rendered rotatable on a roll shaft 47. Said roll shaft 47 issupported by a tension adjusting nut 49 on a lateral plate 48 of thelaminating apparatus C. A tension regulating spring 50 is providedbetween said nut 49 and the core 44, so that the load against filmdrawing can be regulated by said tension adjusting nut 49.

FIG. 3A shows the sheet roll 27 of the laminating film 28 of a firstthickness, wound on a first core 44, while FIG. 3B shows the sheet roll27" of the laminating film 28" of a second thickness, wound on a secondcore 44'. The first core 44 has a straight end face, while the secondcore 44" has a flange 45.

A microswitch 46, provided on the side plate 48 for discriminating thecore, is turned off when the first core 44 is mounted, but is pressed,thereby being turned on, by said flange 45 when the second core 44" ismounted. The difference in thickness of the laminating film 28 or 28"can be identified by the discrimination of the core 44 or 44".

The present embodiment utilizes the discrimination of laminating filmsof two different thicknesses, but it is also possible to discriminatethree or more different thicknesses of the laminating film bycorrespondingly varying the diameter of the flange 45 and increasing thenumber of microswitches 46.

In the following there will be explained the details of the drivingsystem with reference to FIG. 4.

Referring to FIG. 4, which is a developed view of the driving system ofthe laminating apparatus C, a main motor 51 has a motor gear 52 on theoutput shaft whereby the rotation of said main motor 51 is transmittedthrough a motor gear 52, idler gears 60, 54 and a pull roller clutch 59to a pull roller gear 53 and a discharge roller gear 55, therebyrotating the pull roller 36 and the discharge rollers 37. The rotationof said pull rollers 36 and discharge rollers 37 is controlled by saidpull roller clutch 59.

Also the rotation of the main motor 51 is transmitted, through the motorgear 52, idler gears 56, 57, 58, 59', 60' and 61 to a discharge rollergear 62, thereby rotating the, discharge rollers 19.

On the shaft of the idler gear 57 there is provided a pressure rollerclutch 63, which is connected to a pressure roller gear 65, therebycontrolling the rotation of the pressure rollers 30. Similarly the idlergear 59' is provided, on the shaft thereof, with a registration rollerclutch 64 which is connected to a registration roller gear 66 forcontrolling the rotation of the registration rollers 22.

On the shaft of the main motor 51 and opposite to the motor gear 52,there is provided a clock disk 67 having plural slits at a constantpitch, and a clock sensor, consisting of a transmissive photosensor, isprovided in the vicinity of said clock disk 67 for detecting the slits.

In the following there will be explained the operation, in thelaminating apparatus C of the present invention, of laminating thetransfer sheet 10 discharged from the image forming apparatus.

At first a lamination switch, provided in the operation unit 17 on thelaminating apparatus C, is depressed to energize a solenoid (not shown),whereby the flapper 16 assumes the solid-lined state in FIG. 1 to guidethe transfer sheet 10 from the image forming apparatus into thelamination path 21. At the same time the main motor 51 is activated torotate the discharge rollers 19. The registration rollers 22, pressurerollers 30, pull rollers 36 and discharge rollers 37 remain stopped, asthe clutches 64, 65, 59 are deactivated.

When the front end of the transfer sheet 10 is detected by thepre-registration sensor 23, the clock sensor 68 starts to count theclock pulses. When the clock sensor 68 counts a number of clock pulsescorresponding to a time required by the transfer sheet 10 to impinge, atthe front end thereof, on the nip of the registration rollers 22, 22'and to form a predetermined amount of loop, the registration rollerclutch 64 is energized whereby the transfer sheet 10 is introduced intothe transfer path 24 by the registration rollers 22, 22'. The loop ofthe transfer sheet 10 formed in the lamination path 21 is maintaineduntil the rear end of the transfer sheet 10 passes through dischargerollers 14 of the printer B.

When the clock sensor 68 detects that the front end of the transfersheet 10 reaches a position l+α in front of the nip of the pressurerollers 30, 30' in the transfer path 24, wherein l is the distance fromsaid nip to the nearest position of the heaters 30, 30', the pressureroller clutch 63 is turned on whereby the pressure rollers 30, 30' startto rotate. The arrival of the front end of the transfer sheet 10 at aposition of l+α in front of the nip of the pressure rollers 30, 30' canbe, detected, because the distance from the nip of said pressure rollers30, 30' to that of the registration rollers 22, 22' is predetermined, bymeasuring the difference between said distance and l+α by the countingwith the clock sensor 68 from the start of rotation of the registrationrollers 22, 22'. Thus, the front end of the transfer sheet 10 becomespositioned by α behind the front end of the heated portion of theheaters 29, 29', so that the front end of the transfer sheet 10 can besecurely laminated.

Thus the transfer sheet 10, sandwiched between the heated upper andlower laminating films 28, 28', is introduced together with saidlaminating film into the nip of the pressure rollers 30, 30', and issubjected to lamination by the pressure applied by said rollers. Whenthe front end of the thus laminated transfer sheet 10 is detected by thelamination sensor 32, the registration roller clutch 64 and the pressureroller clutch 63 are simultaneously turned off, whereby the movement ofthe transfer sheet 10 is terminated. At the same time the cutter motor(not shown) in the cutter unit 33 is turned on to move the cutter blade34 downwards, thereby cutting the front end portion of the laminatedtransfer sheet 10. When the cutter blade 34 is completely retractedupwards after the cutting, the registration roller clutch 64, pressureroller clutch 63 and pull roller, clutch 59 are turned on to activatethe registration rollers 22, 22', pressure rollers 30, 30' and pullrollers 36, 36'.

Upon detection of the rear end of the transfer sheet 10 by thepre-registration sensor 23, the registration roller clutch 64 is turnedoff to terminate the rotation of the registration rollers 22, 22' whenthe rear end of the transfer sheet 10 passes through the nip thereof.The clock sensor 68 is also used for measuring the amount of movement,from the detection of the rear end of the transfer sheet 10 by thepre-registration sensor 23 to the passing of the rear end of said sheet10 through the nip of the registration rollers 22, 22'.

Upon detection of the rear end of the laminated transfer sheet 10 by thelamination sensor 32, the clock sensor 68 measures the sheet movementcorresponding to the distance from said lamination sensor 32 to thecutter unit 33, and the pressure roller clutch 63 and the pull rollerclutch 59 are turned off to terminate the movement of the laminatedtransfer sheet 10. At the same time, the cutter motor 71 is turned on tocut, with the cutter blade 34, the rear end portion of the laminatedtransfer sheet 10. After said cutting, the pull roller clutch 59 isturned on to activate the pull rollers 36 and the discharge rollers 37,whereby the laminated transfer sheet 10 is discharged and stacked on thelaminate tray 38.

The transfer sheets 10 discharged in succession from the image formingapparatus can be laminated by the repetition of the above-explainedprocedure.

FIG. 5 is a block diagram of a control circuit of the presentembodiment. Said control circuit is principally composed of a knownone-chip microcomputer (MCOM) 70 equipped with a ROM, a RAM etc., andinput ports P0-P7 of said microcomputer 70 are respectively connected tothe aforementioned lamination/non-lamination selector switch 17; theclock sensor 68 for counting the amounts of movement of the rollers 19,22, 22', 30, 30', 36, 36', 37 and 37', the pre-registration sensor 23positioned immediately in front of the registration rollers 22, 22' fordetecting the front and rear ends of the transfer sheet 10; the laminatesensor 32 positioned between the pressure rollers 30, 30' and the cutterunit 33 for detecting the front and rear ends of the laminated transfersheet 10; the image density sensor 26 for detecting the image density ofthe transfer sheet 10 discharged from the image forming apparatus; thecore discriminating switch 46 for discriminating the type of the core ofthe sheet roll 27 or 27' for identifying the thickness of the laminatingfilm 28 or 28'; the sheet thickness sensor 43 for detecting the amountof displacement of the registration roller 22 thereby, identifying thethickness of the transfer sheet 10 passing through the registrationrollers 22, 22'; and the switch 17 for the transfer sheet heater 25.

On the other hand, output ports F0-F7 respectively send signals, throughdrivers D0-D7, for on/off control of the solenoid 70 of the flapper 16for selecting the lamination path or the nonlamination path; on/offcontrol of the main motor 51 and the speed control thereof based on apredetermined speed according to the image density detected by thesensor 26, laminating film thickness detected by the core discriminatingswitch 46 and the thickness of the transfer sheet detected by the sensor43; on/off control of the registration roller clutch 64 for controllingthe rotation of the registration rollers 22, 22'; on/off control of thepressure roller clutch 63 for controlling the rotation of the pressurerollers 30, 30'; on/off control of the pull roller clutch 59 forcontrolling the rotation of the pull rollers 36, 36' and the dischargerollers 37, 37'; on/off control of the sheet heater 25 for heating thetransfer sheet prior to the lamination and temperature control thereforbased on a predetermined temperature according to the change in theimage density of the transfer sheet detected by the sensor 26; on/offcontrol of the lamination heaters 29, 29' for heating the laminatingfilms 28, 28' and control of surface temperature of said laminationheaters 29, 29' based on the image density detected by the sensor 26,film thickness detected by the core discriminating switch 46 and sheetthickness detected by the sensor 43; and on/off control of the cuttermotor for cutting the laminated transfer sheet.

The fetching of input signals, on/off control of the loads, and loadcontrol based on the predetermined values are conducted according to aprogram stored in the ROM of the microcomputer 70.

In the following there will be explained speed control of the main motor51.

In the lamination of the transfer sheet 10, the amount of heatabsorption of said sheet 10 increases with the increase in density ofthe sheet 10. Stated otherwise, more heat is absorbed in a darker sheet.Consequently, if the heating condition of the laminating heaters 29, 29'for the laminating films 28, 28' is constant, the transport speed ofsaid laminating films 28, 28' and of the transfer sheet 10 has to bemade lower (by a slower rotating speed of the main motor 51), in orderto obtain satisfactory lamination. Namely, in consideration of theamount of heat of the laminating films 28, 28' absorbed by the transfersheet 10 at the pressure rollers 30, 30', it is necessary to increasethe heat absorption of the sheet 10 by prolonging the heating time withthe heaters 29, 29'.

Also the transport speed of the laminating films 28, 28' and thetransfer sheet 10 has to be made lower for a larger thickness of thetransfer sheet 10, as the amount of heat absorption of the transfersheet 10 becomes larger for a larger thickness.

Furthermore, said transport speed has to be made lower for a largerthickness of the laminating films 28, 28', since the amount of heatabsorption of said films likewise increases.

Consequently, in the laminating apparatus C of the present embodiment,the transport speed of the transfer sheet 10 and the laminating films28, 28' can be controlled according to the image density and thicknessof the transfer sheet 10, and the thickness of the laminating films 28,28', by feedback of the data from the density detecting sensor 26, sheetthickness sensor 43 and core discriminating switch 46 to the rotatingspeed of the main motor 51.

More specifically, as shown in FIG. 5, at least one of an image densitysignal detected by the density detecting sensor 26, a laminating filmthickness signal detected by the core discriminating switch 46, and asheet thickness signal detected by the sheet thickness sensor 43 issupplied to the control circuit 70, which in response discriminates thetotal heat capacity of the, transfer sheet and the laminating films.Thus the control circuit 70 controls the rotating speed of the mainmotor 51, thereby regulating the transport speed of the transfer sheetand the laminating films, in order to provide the laminating films, bymeans of the laminating heaters 29, 29', with thermal energy enough forlamination corresponding to said total heat capacity. Thus, for a largeor small total heat capacity, the transport speed is respectivelydecreased or increased in order to provide the laminating films with alarger or smaller amount of thermal energy.

In the following there will be explained temperature control of thelaminating heaters 29, 29'.

Just like the speed control of the main motor 51 explained above, thetemperature of the laminating heaters 29, 29' has to be controlledaccording to the image density of the transfer sheet 10 and thickness ofsaid sheet 10 and of the laminating films 28, 28' because the amount ofheat absorption by the laminating films 28, 28' varies. Morespecifically, the temperature of said heaters 29, 29' has to be elevatedfor increasing the amount of heat energy supply as the image density,thickness of the transfer sheet 10 or thickness of the laminating films28, 28' increases.

Consequently, in the laminating apparatus C of the present embodiment,the temperature of the laminating heaters 29, 29' is feedback controlledby the data from the density detecting sensor 26, sheet thickness sensor43 and core discriminating switch 46.

More specifically, as shown in FIG. 5, at least one of the image densitysignal detected by the density detecting sensor 26, the laminating filmthickness signal detected by the core discriminating switch 46 and thesheet thickness signal detected by the sheet thickness sensor 43 issupplied to the control circuit 70, which in response discriminates thetotal heat capacity of the transfer sheet and the laminating films. Thusthe control circuit 70 controls the temperature of the laminatingheaters 29, 29', in order to provide the laminating films, by means ofthe laminating heaters 29, 29', with thermal energy enough forlamination corresponding to said total heat capacity. Thus, for a largeor small total heat capacity, the temperature of the laminating heaters29, 29' is respectively increased or decreased for increasing ordecreasing the amount of thermal energy given to the laminating films.

The above-explained transport speed control and heater controlcorresponding to the thermal capacity of the transfer sheet and thelaminating films may be employed singly or in combination.

In the following there, will be explained on/off control and temperaturecontrol of the transfer sheet heater 25.

In image formation with ink in an image forming apparatus to beexplained later in relation to FIG. 6, the transfer sheet 10 isdischarged from said apparatus in a wet state with undried ink. If thesheet is laminated in such wet state, moisture will be sealed betweenthe upper and lower laminating films 28, 28', thus forming bubbles andundesirably affect the appearance of the laminate. It is thereforenecessary to heat the transfer sheet 10 prior to lamination, therebyevaporating the moisture therein.

However, excessive heating will cause curling of the transfer sheet 10,eventually leading to creases or curling of the obtained laminate. Thewet level of the sheet 10 depends on the image density, and a higherimage density is more inconvenient for lamination.

In the laminating apparatus of the present embodiment, therefore, theheating temperature can be automatically controlled according to theimage density detected in advance by the density detecting sensor 26.More specifically, the temperature of the transfer sheet heater 25 isset higher or lower respectively for a higher or lower image density. Onthe other hand, certain image forming apparatus form the image withtoner instead of ink, and the transfer sheet in such image formingapparatus is discharged in a dry state. In such case the heating priorto lamination is unnecessary. Consequently the operator can turn off theheater with a switch provided in the operation unit 17.

The transfer sheet heater is controlled in the following manner. Theimage density signal detected by the density detecting sensor 26 shownin FIG. 5 is supplied to the control circuit 70, which in responsecontrols the temperature of the transfer sheet heater 25. In theforegoing embodiment there are employed heaters for drying the transfersheet, but the drying may also be achieved by sending air to the surfaceof the transfer sheet for example with a fan, and the revolution of saidfan is controlled in such case. Also the image density may be detectedby a sensor for detecting the density of the original read by the readerA.

As an alternative method for drying the transfer sheet according to thewet level thereof prior to lamination, it is also possible to vary thepassing time of the transfer sheet 10 through the heater 25. In suchcase, in response to the image density signal supplied from the densitydetecting sensor 26, the control circuit 70 controls the main motor 51in such a manner that the transport speed of the transfer sheet by theregistration rollers 22, 22' becomes lower as the image density,increases. At a lower transport speed, the transfer sheet 10 stays onthe heater 25 longer thereby drying better. Furthermore, the temperaturecontrol of the heater 25 and the control of the transport speed may beemployed in combination.

FIG. 6 shows an embodiment in which the image forming means of theprinter B of the foregoing embodiment is replaced by an ink jetrecording apparatus.

Referring to FIG. 6, there are shown rollers 101, 102 for transportingthe transfer sheet; an ink jet head 103 for image formation by emittingink droplets onto a sheet; and a carriage 104 supporting said ink jetrecording head 103 and adapted to reciprocate along a guide member 105in a direction perpendicular to the sheet transporting direction.

FIG. 7 shows a bubble jet recording head, as an example of the ink jetrecording head, in an exploded perspective view.

Referring to FIG. 7, a heater board 111 is composed of a siliconsubstrate, provided thereon with electrothermal converters (dischargeheaters 112), and electrodes 113 for example of aluminum for supplyingsaid electrothermal converters with electric power. A recording head 103is formed by adhering, to said heater board 111, a cover plate 115having partitions for separating liquid paths 114 (nozzles) for therecording liquid. Also in a predetermined position of the apparatus, areplaceable ink cartridge is mounted for supplying said recording head103 with the ink (recording liquid).

The ink supplied from said ink cartridge through a pipe is introduced,through a supply aperture 116 provided in the cover plate 115,. into acommon liquid chamber 117 of the recording head 103, and is furtherguided from said chamber into the nozzles 114. Said nozzles 114 arerespectively provided with ink discharge apertures 118, which arearranged on a face of the recording head 103 opposite to the recordingsheet, with a constant pitch in the sheet transporting direction.

In the present embodiment, recording is achieved by discharging the inkfrom the recording head 103 in synchronization with the movement of thecarriage 104.

The principle of ink discharge in the aboveexplained bubble jetrecording method is disclosed for example in the U.S. Pat. Nos.4,723,129 and 4,740,796.

Said principle will be briefly explained with reference to FIGS. 8A to8G. In a stationary state shown in FIG. 8A, the ink 120 filled in thenozzle 114 is in equilibrium of the surface tension and the externalpressure at the face of the discharge opening. In order to discharge theink 120 from this state, electric power is supplied to theelectrothermal converter 112 in the nozzle 114, thereby inducing rapidtemperature increase exceeding nucleus boiling in the ink in said nozzle114. Thus, as shown in FIG. 8B, the ink positioned adjacent to theelectrothermal converter 112 generates small bubbles by heating, and isgasified to generate membrane boiling, whereby said bubbles 121 growrapidly as shown in FIG. 8C.

When the bubble 121 grows to a maximum as shown in FIG. 8D, an inkdroplet is pushed out from the discharge opening of the nozzle 114. Whenthe power supply to the electrothermal converter 112 is terminated, thebubble 121 contracts as shown in FIG. 4E by cooling with the ink 120 inthe nozzle 114, and an ink droplet is discharged by the growth andcontraction of said bubble. The electrothermal converter 112 is rapidlycooled in contact with the ink, whereby the bubble 121 either disappearsor contracts to a negligible volume, as shown in FIG. 8F. Upon saidcontraction of the bubble 121 the ink is replenished by capillary actioninto the nozzle 114 from the common liquid chamber 117, as shown in FIG.8G, thereby preparing for the next electric power supply.

Thus an ink image is recorded on the recording sheet, by energization ofthe electrothermal converters 112 according to image signals and insynchronization with the reciprocating motion of the carriage 104.

In the above-explained ink jet recording method, recovery means ispreferably provided at an end portion of the moving range of thecarriage. Said recovery means serves to prevent ink drying orsolidification in the vicinity of discharge openings of the recordinghead, 103, by covering the ink discharge face of said recording head 103in the non-recording state. Also said recovery means may be connected toa pump for sucking ink out of the discharge openings, for the purpose ofrectifying or preventing ink discharge failure.

Also in the embodiment shown in FIGS. 6 to 8, as in the foregoingembodiments, the control circuit shown in FIG. 5 controls the transportspeed of the recording sheet, the laminating heaters 29, 29' and thesheet heater 25.

In the foregoing embodiments there are provided the laminating films onboth sides of the transfer sheet, but there may be provided only onelaminating film on a side (image bearing face) of the transfer sheet.

Also the laminating heaters 29, 29' and the sheet heater 25 arecontrolled by temperature in the foregoing embodiments, but the methodof control is not limited to such embodiments and can be controlled inany manner as to vary the amount of thermal energy supply. For example,the amount of thermal energy supply may be varied by varying the numberof energized ones in plural heaters.

Also in the foregoing embodiments the laminating films are pressed tothe transfer sheet with heating, but the present invention is applicablelikewise to films capable of lamination by pressure only, withoutheating.

FIG. 9 shows another embodiment, which is different from the foregoingembodiments shown in FIGS. 1 to 6, in that pressure-sensitive adhesiveis employed in one of the laminating films.

In FIG. 9, a laminating film roll 28 employs a heat-sensitive adhesivecoated on the external surface, while a laminating film roll 28' employspressure while sensitive adhesive coated on the external surface. Alaminating heater 29 is provided for heating the heat-sensitivelaminating film 28, which becomes adhesive upon heating. Said heater 29has a curved surface for heating the film over a wide area. Thetemperature of said heater is rendered variable by a sensor provided atthe surface of said heater.

Pressure rollers 30, 30' effect the lamination of the recording sheet,by pressing said sheet between the laminating film 28 heated by thelaminating heater 29 and the laminating film 28' coated with thepressuresensitive adhesive. Said laminating film 28' coated with thepressure-sensitive adhesive becomes adhesive by the pressure exerted bythe pressure rollers 30, 30'. A guide roller 71 is provided for guidingthe laminating film 28'.

In the present embodiment, the heat-sensitive laminating film withglossy surface is adhered to the image bearing face of the recordingsheet, while the non-glossy pressure-sensitive laminating film of lowrigidity, not requiring heating, is adhered to the image-free face,which is less affected, by the drawbacks of the laminating film, wherebythe electric power consumption of the laminating apparatus can bereduced without undesirable influence on the image bearing face.

Other structures and controls of the present embodiment are same asthose in the foregoing embodiments shown in FIGS. 1 and 6.

What is claimed is:
 1. A laminating apparatus, comprising:laminatingfilm transporting means for transporting at least one laminating film insuch a manner that the laminating film is superposed with at least onesurface of a sheet to be laminated; pressing means for pressing thesheet and the laminating film in a mutually superposed state; heatingmeans for heating said laminating film; heat capacity signal generatingmeans for generating a signal indicative of the heat capacity of eitherone or both of the laminating film and the sheet; and control means forcontrolling at least one of said heating means and said laminating filmtransporting means based on the signal output from said heat capacitysignal generating means.
 2. A laminating apparatus according to claim 1,wherein said laminating film transporting means is adapted to supportsaid laminating film and the sheet in a mutually superposed state.
 3. Alaminating apparatus according to claim 2, wherein said laminating filmtransporting means comprises a pair of rollers.
 4. A laminatingapparatus according to claim 3, wherein said heating means is providedin at least one of said pair of rollers, thereby heating the laminatingfilm by means of said roller heated by said heating means.
 5. Alaminating apparatus according to claim 1, wherein said heating means isadapted to heat the laminating film prior to pressing by said pressingmeans.
 6. A laminating apparatus according to claim 1, wherein saidcontrol means is adapted to control said heating means in such a manneras to increase the amount of thermal energy supply as the heat capacityof the sheet or the laminating film increases.
 7. A laminating apparatusaccording to claim 1, wherein said control means is adapted to controlsaid laminating film transporting means in such a manner as to decreasethe transporting speed as the heat capacity of the sheet or thelaminating film increases.
 8. A laminating apparatus according to claim1, wherein said heat capacity signal generating means comprises densitydetecting means for detecting the density of an image formed on thesheet.
 9. A laminating apparatus according to claim 8, wherein saidcontrol means is adapted to control said heating means in such a manneras to increase the amount of thermal energy supply as the density of theimage of the sheet, as detected by said density detecting means,increases.
 10. A laminating apparatus according to claim 8, wherein saidcontrol means is adapted to control said laminating film transportingmeans in such a manner as to decrease the transporting speed as thedensity of the image of the sheet, as detected by said density detectingmeans, increases.
 11. A laminating apparatus according to claim 1,wherein said heat capacity generating means comprises sheet thicknessdetecting means for detecting the thickness of the sheet.
 12. Alaminating apparatus according to claim 11, wherein said control meansis adapted to control said heating means in such a manner as to increasethe amount of thermal energy supply as the sheet thickness detected bysaid sheet thickness detecting means increases.
 13. A laminatingapparatus according to claim 11, wherein said control means is adaptedto control said laminating film transporting means in such a manner asto decrease the transporting speed as the sheet thickness detected bysaid sheet thickness detecting means increases.
 14. A laminatingapparatus according to claim 1, wherein said heat capacity generatingmeans comprises laminating film thickness detecting means for detectingthe thickness of the laminating film.
 15. A laminating apparatusaccording to claim 14, wherein said control means is adapted to controlsaid heating means in such a manner as to increase the amount of thermalenergy supply as the thickness of the laminating film detected by saidlaminating film thickness detecting means increases.
 16. A laminatingapparatus according to claim 14, wherein said control means is adaptedto control said laminating film transporting means in such a manner asto decrease the transporting speed as the thickness of the laminatingfilm detected by said laminating film thickness detecting meansincreases.
 17. An image forming apparatus, comprising:image formingmeans for forming an image on a sheet; sheet transporting means fortransporting the sheet subjected to image formation by said imageforming means; laminating film transporting means for transporting atleast one laminating film in such a manner that the film is superposedwith at least the image bearing face of the sheet transported by saidsheet transporting means; pressing means for pressing the sheet and thelaminating film in a mutually superposed state; heating means forheating the laminating film; heat capacity signal generating means forgenerating a signal indicative of the heat capacity of either one orboth of the laminating film and the sheet; and control means forcontrolling at least one of said heating means and said laminating filmtransporting means based on the signal output from said heat capacitysignal generating means.
 18. An image forming apparatus according toclaim 17, wherein said image forming means comprises an image bearingmember and is adapted to transfer an image of said image bearing memberonto said sheet.
 19. An image forming apparatus according to claim 17,wherein said image forming means comprises a recording head for formingan image on the sheet by ink discharge.
 20. An image forming apparatusaccording to claim 19, wherein said recording head is adapted to effectink discharge by thermal energy.
 21. An image forming apparatusaccording to claim 17 wherein said heat capacity signal generating meanscomprises density detecting means for detecting the density of the imageformed on the sheet.
 22. An image forming apparatus according to claim21, wherein said control means is adapted to control said heating meansin such a manner as to increase the amount of thermal energy supply asthe image density of the sheet detected by said density detecting meansincreases.
 23. An image forming apparatus according to claim 21, whereinsaid control means is adapted to control said laminating filmtransporting means in such a manner as to decrease the transportingspeed thereof as the image density of the sheet detected by said densitydetecting means increases.
 24. An image forming apparatus according toclaim 17, wherein said heat capacity signal generating means comprisessheet thickness detecting means for detecting the thickness of thesheet.
 25. An image forming apparatus according to claim 24, whereinsaid control means is adapted to control said heating means in such amanner as to increase the amount of thermal energy supply as the sheetthickness detected by said sheet thickness detecting means increases.26. An image forming apparatus according to claim 24, wherein saidcontrol means is adapted to control said laminating film transportingmeans in such a manner as to decrease the transporting speed thereof asthe sheet thickness detected by said sheet thickness detecting meansincreases.
 27. An image forming apparatus according to claim 17, whereinsaid heat capacity signal generating means comprises laminating filmthickness detecting means for detecting the thickness of the laminatingfilm.
 28. An image forming apparatus according to claim 27, wherein saidcontrol means is adapted to control said heating means in such a manneras to increase the amount of thermal energy supply as the thickness oflaminating film detected by said laminating film thickness detectingmeans increases.
 29. An image forming apparatus according to claim 27,wherein said control means is adapted to control said laminating filmtransporting means in such a manner as to decrease the transportingspeed thereof as the thickness of laminating film detected by saidlaminating film thickness detecting means increases.